doi:10.1038/nindia.2013.142 Published online 25 October 2013
A gene isolated from a fungus discovered in India's Thar desert can potentially revolutionise agriculture in salt affected soils around the world, a research at the International Centre for Genetic Engineering and Biotechnology (ICGEB) in New Delhi suggests .
Soil salinity problems are widespread around the globe hampering cultivation of crop plants. Salt in soil leads to molecular damage, growth inhibition and even death of plants. Unregulated large-scale irrigation programmes, poor soil management and marine aquaculture are major reasons for the spread of soil salinity. Approximately 3.2 million square kilometre land worldwide is affected by salinity problems, as per the soil map prepared by FAO/UNESCO. The research at ICGEB has shown the desert fungus Piriformospora indica holds the key to make these lands cultivable.
"The fungus symbiotically interacts with the roots of many plant species and promotes growth, development and seed production," Neel Sarovar Bhavesh, one of the authors of the study, told Nature India. "Although the symbiotic relation of P. indica fungus is known to provide salt stress tolerance to plants, the molecular mechanism for such action was till now largely unknown making it difficult to exploit this indigenous organism for increasing agricultural productivity," he said.
That obstacle has now been overcome. The scientists claim to have demonstrated for the first time a direct evidence of countering salinity stress in tobacco plant by genetic modification of the plant using a single gene from P. indica. "The cyclophilin A-like gene of P. indica was used to generate transgenic tobacco plants that were able to grow in soil containing very high salt (12 grams per litre of sodium chloride).
"The genetically modified (GM) plants had better plant growth, higher seed yield and early flowering and their overall performance was unaffected in the presence of 12 grams per litre NaCl while normal (unmodified) plants did not survive beyond 3 grams per litre of salt," Bhavesh, who jointly led the study with Narendra Tuteja, said. The team also comprised of phD students Harshesh Bhatt and Dipesh Trivedi.
To understand at a molecular level how this single gene helps plants to survive at very high salt conditions, the ICGEB team determined the atomic-resolution structure of the protein (PiCypA) expressed by the gene from P. indica. "Using X-ray crystallography, solution-state NMR spectroscopy and calorimetry we identified and explained a novel RNA binding activity at a molecular level," the researchers said in their report. The PiCypA protein, according to Bhavesh, stabilizes RNAs (messengers of genetic information) during stress conditions, which is essential for plant health. Generally, RNAs get destroyed under stress conditions resulting in poor synthesis of proteins that alters the plant metabolism leading to death of plants, he said. "This study suggests that PiCypA may play a crucial role in stress protection presumably through its active role in maintenance of both RNA and protein structure during stress."
The findings open up new areas for tinkering cellular machinery in plants to counteract salinity stress tolerance and have a great potential for crop improvement especially in coastal areas where agricultural lands have become infertile, the report concludes.